JP2014077047A - Core-shell type silica nanoparticles and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide core-shell type silica nanoparticles formed by making an aliphatic polyamine having a primary amino group and/or a secondary amino group form a composite with silica in a shell layer, especially to provide fine core-shell type silica nanoparticles having excellent monodispersity and a diameter of several tens of nm or less; and to provide a simple and efficient method for producing the particles.SOLUTION: Provided is a method for producing core-shell type silica nanoparticles comprising steps of forming aggregates comprising a core layer containing a hydrophobic organic segment (a2) as a main component and a shell layer containing an aliphatic polyamine chain (a1) as a main component by mixing a copolymer (A) and an aqueous medium, the copolymer comprising an aliphatic polyamine chain (a1) having a primary amino group and/or a secondary amino group and a hydrophobic organic segment (a2); and a step of performing a sol-gel reaction of silica source using the aggregates as a template; and the particles.

Description

  The present invention relates to a core-shell type silica nanoparticle having an organic component as a core portion and containing silica and an organic component in a shell layer and a simple production method thereof.

  In recent years, research and development of functional nanostructured materials has been actively conducted, and in various industrial fields, research on nanostructure, organic-inorganic composite, and hierarchical structure of materials that become materials has been conducted. Particularly, nanoparticles having a core-shell structure, for example, core-shell type silica nanoparticles having a polymer as a core, can be used as drug delivery systems, sustained-release cosmetics, diagnostic materials, optical materials, hollow material formation, and the like. . Silica nanoparticles having such a core-shell structure have been studied in various ways such as introduction of functional organic components and control of particle size or structure depending on characteristics required in various applications.

  Synthesis methods of core-shell type silica nanoparticles having a polymer as a core can be roughly classified into an emulsion polymerization method and a template method. The emulsion polymerization method is a method in which a hydrophobic monomer is polymerized in the presence of silica nanoparticles (sol) and adhered to the surface of the polymer particles formed by silica nanoparticles to form a silica shell (for example, see Non-Patent Document 1). ). The silica shell thus obtained is a layer formed by physically assembling silica nanoparticles, and thus is structurally unstable. For example, after removing the core polymer, the shell layer collapses. May end up. Core-shell type silica nanoparticles having a polymer synthesized by an emulsion polymerization method as a core can be applied as an organic-inorganic composite coating or film, but application as core-shell type nanoparticles is difficult.

  On the other hand, the template method is a method of forming a silica shell by using a synthesized polymer nanoparticle as a template and performing a silica sol-gel reaction on the surface of the particle. In many of the template methods, silica is deposited on the surface of polymer latex particles in the presence of ammonia based on the Stover method, which is a general method for producing silica nanoparticles (see, for example, Patent Documents 1 and 2). However, these methods require a high ammonia concentration when performing the sol-gel reaction and have a large environmental load and low productivity. Further, the core-shell type silica nanoparticles obtained in Patent Documents 1 and 2 are those in which silica is formed on the surface of the polymer particles as a shell, and an organic component is not introduced into a silica matrix. Furthermore, since the particle shape of the polymer latex particles used as the template is 50 nm or more, it was difficult to synthesize core-shell type silica nanoparticles having a particle size of 50 nm or less.

  In recent years, synthesis of nanosilica imitating biosilica has been actively carried out, and synthesis of silica nanoparticles under mild conditions in an aqueous medium has been studied by using polyamines as templates. For example, it has been studied to synthesize spherical silica in an aqueous medium using a polypeptide having a polyamine extracted from biosilica, a synthetic polyallylamine, a cationic polymer, or a block copolymer (for example, patents). References 3-4, non-patent references 2-6). For example, in Patent Document 3, a diblock copolymer micelle made of amino acrylate is used as a template, and a silica sol-gel reaction is performed in the shell layer of the micelle, whereby a cationic polymer is used as a core and the particle size is 35 nm. Core-shell type silica nanoparticles are disclosed. Unlike silica deposition based on the Stover method, a silica layer formed using polyamine micelles as a template is an organic-inorganic composite in which an acrylate-based tertiary polyamine is introduced into a silica matrix.

  However, these methods have good monodispersibility that can be used in a wide range of fields such as transparent resin fillers, and it is still difficult to produce core-shell type silica nanoparticles having a particle size of 30 nm or less. The polyamines introduced into the silica matrix are only aromatic polyamines (Non-patent Document 4) or acrylate-based tertiary polyamines (Patent Document 3). In the conventional silica nanoparticle synthesis technology, an aliphatic polyamine having a primary particle group and / or a secondary amino group in the matrix of the shell layer silica having a uniform particle size and a particle size of 5-30 nm can be controlled. The introduced ultrafine core-shell type silica nanoparticles have not been synthesized.

Special table 2009-504632 gazette JP 2011-42527 A Special table 2010-502795 gazette JP 2006-306711 A

A. Schmide et al. , Macromolecules, 2009, 42, 3721. D. Morse, Nature, 2000, 403, 289. N. Kroger, et al. , Science, 2002, 298, 584 A. Kanal, et al. , J .; Am. Chem. Soc. , 2007, 129, 1534. J. et al. Yang, et al. , Chem. Mater. , 2008, 20, 2875. M.M. Pi, et al. , Colloids and Surfaces B Biointerfaces, 2010, 78, 193.

  In view of the above circumstances, the problem to be solved by the present invention is to provide core-shell type silica nanoparticles obtained by complexing an aliphatic polyamine having a primary amino group and / or a secondary amino group with silica in a shell layer. In particular, to provide fine core-shell type silica nanoparticles having excellent monodispersibility and a particle size of several tens of nm or less, and to provide a simple and efficient method for producing the particles. is there.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a copolymer having an aliphatic polyamine having a primary amino group and / or a secondary amino group and a hydrophobic organic segment in an aqueous solvent. When dissolved, an aggregate having a core-shell structure can be easily obtained, and the aggregate is used as a template that catalyzes silica deposition, and the sol-gel reaction of silica source is selectively advanced in the shell layer of the aggregate. In order to complete the present invention, it is found that a core-shell type silica nanoparticle having a core layer mainly composed of a hydrophobic organic segment part, a shell layer formed by combining an aliphatic polyamine part and silica is obtained. It came.

  That is, the present invention relates to the hydrophobic organic segment (a2) of the copolymer (A) having an aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group and a hydrophobic organic segment (a2). A core-shell type silica nanoparticle comprising: a core layer mainly composed of a portion; and a shell layer composed of a composite composed mainly of the aliphatic polyamine chain (a1) and silica (B). And a manufacturing method thereof.

  The core-shell type silica nanoparticles obtained in the present invention are designed to have a self-organization of a copolymer having an aliphatic polyamine and a hydrophobic organic segment. Ultrafine silica nanoparticles in the 5-30 nm range. Further, unlike the conventional core-shell type silica fine particles, the shell layer of the core-shell type silica nanoparticles of the present invention has a hybrid structure at a molecular level in which aliphatic polyamines are uniformly complexed in a matrix formed by silica. Have The core-shell type silica nanoparticles have a chemical or physical function derived from polyamine. For example, since polyamines are strong ligands, metal ions can be concentrated in silica. In addition, since polyamine is a reducing agent, it is possible to synthesize silica / noble metal composite nanoparticles by reducing concentrated noble metal ions to metal atoms. In addition, since polyamine is a cationic polymer, it has functions such as sterilization and virus resistance. Therefore, the nanoparticles can also discover these functions. Therefore, the core-shell type silica nanoparticles of the present invention can be used in drug delivery systems, sustained-release cosmetics, diagnostic materials, optical materials, resin fillers, abrasive fillers, metal ions / nanometals / metal oxide carriers, catalysts, and prevention agents. Application development in many areas such as fungicide is possible.

  In the production method of the present invention, by using a reaction method imitating silica synthesis in a biological system, it is excellent in monodispersity and has a polyamine function under mild reaction conditions such as low temperature and neutrality. Ultra fine core-shell type silica nanoparticles can be produced in a short time. The manufacturing method has a low environmental load, a simple production process, and a structural design corresponding to various uses.

2 is a transmission electron micrograph of spherical core-shell type silica nanoparticles obtained in Example 1. FIG. 6 is a transmission electron micrograph of string-like core-shell type silica nanoparticles obtained in Example 5. FIG. 6 is a transmission electron micrograph of core-shell type silica nanoparticles having a plurality of cores obtained in Example 8. FIG. 2 is a transmission electron micrograph of core-shell type silica nanoparticles having a plurality of cores obtained in Example 11. FIG. 2 is a transmission electron micrograph of silica nanoparticles obtained in Example 12. 2 is a transmission electron micrograph of core-shell type silica nanoparticles obtained in Example 17. FIG.

  In order to build silica (silicon oxide) into a designed nanostructure / shape from a sol-gel reaction in the presence of water, three important conditions are considered essential. It is (1) a template for inducing shape / structure, (2) a scaffold for conducting a sol-gel reaction, and (3) a catalyst for hydrolyzing and polymerizing a silica source.

  In the present invention, in order to satisfy the above three elements, the copolymer (A) having an aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group and a hydrophobic organic segment (a2). It is characterized by using. When the copolymer (A) is dissolved in an aqueous solvent, an aggregate can be easily formed by molecular self-assembly. The aggregate has a core-shell structure, the core is a hydrophobic organic segment (a2), and the shell is a polyamine chain (a1).

  The present invention uses the aggregate having the core-shell structure obtained as described above as a template, and in a solvent, the sol-gel reaction of silica source is carried out in the shell layer of the aggregate by the catalytic effect of the aliphatic polyamine chain (a1). The present inventors have found that ultrafine core-shell type silica nanoparticles excellent in monodispersity can be produced by selectively performing an aliphatic polyamine chain (a1) in a silica matrix.

[Copolymer (A) having aliphatic polyamine chain (a1) having primary amino group and / or secondary amino group and hydrophobic organic segment (a2)]
In the present invention, the aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group in the copolymer (A) is dissolved in an aqueous solvent to form the hydrophobic organic segment (a2) as a core. If it can form the aggregate | assembly to make, it will not specifically limit, For example, a branched polyethyleneimine chain | strand, a linear polyethyleneimine chain | strand, a polyallylamine chain | strand etc. can be used. From the viewpoint of efficiently producing the target silica nanoparticles, it is desirable to use a branched polyethyleneimine chain. In addition, the molecular weight of the polyamine chain (a1) portion is not particularly limited as long as it is within a range that can form an aggregate in a balanced manner with the hydrophobic organic segment (a2), but from the viewpoint of suitably forming an aggregate. The number of repeating units of the polymer units of the polyamine chain portion is preferably in the range of 5 to 10,000, particularly preferably in the range of 10 to 8,000.

  Further, the molecular structure of the aliphatic polyamine chain (a1) portion is not particularly limited, and for example, a linear shape, a branched shape, a dendrimer shape, a star shape, or a comb shape can be preferably used. It is preferable to use a branched polyethyleneimine chain from the viewpoint of production cost and the like because an aggregate used as a template for silica deposition can be efficiently formed.

  Even if the skeleton of the aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group is composed of only one kind of amine polymer unit, a polyamine chain composed of a copolymer of two or more kinds of amine units ( Copolymer). Further, in the skeleton of the aliphatic polyamine chain (a1), polymerized units other than amines may be present as long as the aggregate can be formed in an aqueous medium. From the viewpoint of suitably forming an aggregate, the proportion of other polymerized units is preferably contained in the amine skeleton of the aliphatic polyamine chain (a1) at 50 mol% or less, and at 30 mol% or less. More preferably, it is most preferably 15 mol% or less.

  The hydrophobic organic segment (a2) in the copolymer (A) is not particularly limited as long as it can form a stable aggregate having the hydrophobic organic segment (a2) as a core by a hydrophobic action in an aqueous solvent. And a segment made of an alkyl compound and a segment made of a hydrophobic polymer such as polyacrylate, polystyrene, or polyurethane. In the case of an alkyl compound, a compound having an alkylene chain having 5 or more carbon atoms is preferable, and a compound having an alkylene chain having 10 or more carbon atoms is more preferable. The length of the hydrophobic polymer chain is not particularly limited as long as the aggregate can be stabilized in the nano size, but the number of repeating units of polymer units of the polymer chain is 5- A range of 10,000 is preferable, and a range of 5-1000 is particularly preferable.

  The method for bonding the hydrophobic organic segment (a2) to the aliphatic polyamine (a1) is not particularly limited as long as it is a stable chemical bond, and, for example, bonded by coupling to the terminal of the polyamine, or It may be bonded to the polyamine skeleton by grafting. One hydrophobic organic segment (a2) may be bonded to one polyamine chain (a1), or a plurality of hydrophobic organic segments (a2) may be bonded.

  The ratio of the aliphatic polyamine chain (a1) and the hydrophobic organic segment (a2) in the copolymer (A) is not particularly limited as long as a stable aggregate can be formed in the aqueous medium. From the viewpoint of easily forming an aggregate, the proportion of the polyamine chain is preferably in the range of 10-90% by mass, more preferably in the range of 30-70% by mass, and in the range of 40-60% by mass. Most preferably.

  As the copolymer (A) used in the present invention, it is possible to modify the copolymer (A) by appropriately selecting molecules having various functionalities. The modification may be modification to the aliphatic polyamine (a1) or modification to the hydrophobic organic segment (a2). For the modification to the copolymer (A), any functional molecule may be introduced as long as a stable association can be formed in an aqueous solvent, and the association of the modified copolymer (A) is used as a template. As a result of depositing silica, core-shell type silica nanoparticles having an arbitrary functional molecule introduced can be obtained. From such a viewpoint, it is particularly preferable to modify with a fluorescent compound, and when the fluorescent compound is used, the obtained core-shell type silica nanoparticles also exhibit fluorescence and are suitable for various application fields. It can be used.

[Core-shell type silica nanoparticles]
The core-shell type silica nanoparticles of the present invention comprise a core layer mainly composed of a hydrophobic organic segment (a2) portion, and a composite composed mainly of an aliphatic polyamine chain (a1) and silica (B). A core-shell type silica nanoparticle having a shell layer. Here, the main component means that no components other than the copolymer (A) and silica (B) are contained unless the third component is intentionally introduced, and the copolymer in an aqueous medium. In the formation of the aggregate in (A), for example, the core part may contain a part of the polyamine chain (a1) or the shell layer part may contain a part of the hydrophobic organic segment (a2). Is. In particular, the shell layer in the particles is an organic-inorganic composite in which an aliphatic polyamine chain (a1) is combined with a matrix formed by silica.

  The core-shell type silica nanoparticles of the present invention have a particle size in the range of 5 to 100 nm, and particularly core-shell type silica nanoparticles in the range of 5 to 50 nm can be suitably obtained. The particle diameter of the core-shell type silica nanoparticles can be adjusted by the preparation of the aggregate (for example, the type, composition, molecular weight, etc. of the copolymer (A) to be used), the type of silica source, the sol-gel reaction conditions, and the like. Further, since the core-shell type silica nanoparticles are formed by self-organization of molecules, they have extremely excellent monodispersity, and in particular, the width of the particle size distribution is ± 15% with respect to the average particle size. It is possible to:

  The core-shell type silica nanoparticles of the present invention can have a spherical shape or a string shape with an aspect ratio of 2 or more. Also, core-shell type silica nanoparticles having a plurality of cores in one particle can be synthesized. The shape and structure of the particles can be adjusted by the composition of the copolymer (A), the adjustment of the aggregate, the type of silica source, the sol-gel reaction conditions, and the like.

  The content of silica in the core-shell type silica nanoparticles of the present invention can be varied within a certain range depending on the reaction conditions and the like, and is generally 30 to 95% by mass of the entire core-shell type silica nanoparticles. , Preferably it can be set as the range of 60-90 mass%. The content of silica includes the content of the aliphatic polyamine chain (a1) in the copolymer (A) used in the sol-gel reaction, the amount of aggregate, the type and amount of silica source, the sol-gel reaction time and temperature, etc. It can be changed by changing.

  The core-shell type silica nanoparticles of the present invention can contain polysilsesquioxane in the core-shell type silica nanoparticles by performing a sol-gel reaction using organosilane after silica deposition. Such a core-shell type silica nanoparticle containing polysilsesquioxane exhibits excellent monodispersity and high sol stability in a solvent. Moreover, even if it dries, it can be re-dispersed in the medium again. This is a characteristic that is greatly different from that once a conventional silica nanoparticle dispersion is dried, it is difficult to redisperse into a particulate form. In the case of silica fine particles obtained by a conventional Stover method or the like, redispersibility in a medium is difficult unless the surface of the obtained fine particles is chemically modified with a substance such as a surfactant. Since secondary agglomeration or the like occurs, a pulverization treatment for obtaining nano-level ultrafine particles is often necessary.

  Moreover, the core-shell type silica nanoparticles of the present invention can adsorb metal ions highly concentrated by the aliphatic polyamine chain (a1) present in the silica matrix of the shell layer. Further, since the aliphatic polyamine chain (a1) is cationic, the core-shell type silica nanoparticles of the present invention can adsorb and immobilize various ionic substances such as anionic biomaterials. Furthermore, the hydrophobic organic segment (a2) portion in the copolymer (A) can be variously selected depending on the functionality, and the structure can be easily controlled, so that various functions can be imparted.

  For example, the function may be given by immobilizing a fluorescent substance. For example, when a small amount of a fluorescent substance, pyrenes, porphyrins or the like is introduced into the aliphatic polyamine chain (a1), the functional residue is taken into the shell layer of the silica nanoparticles. Furthermore, by using a mixture of a small amount of fluorescent dyes such as porphyrins, phthalocyanines, pyrenes having acidic groups, for example, carboxylic acid groups and sulfonic acid groups, in the base of the aliphatic polyamine chain (a1), silica nano These fluorescent substances can be incorporated into the shell layer in the particles. Similarly, the functional substance is selectively fixed to the hydrophobic organic segment (a2), an aggregate is formed, and silica is precipitated to selectively incorporate the functional substance into the core layer of the silica nanoparticles. It can also be made.

  The silica nanoparticles of the present invention can be dried and used as a powder, and can also be used as a filler for other compounds such as resins. It is also possible to blend into other compounds as a dispersion or sol obtained by redispersing the dried powder in a solvent.

[Method for producing core-shell type silica nanoparticles]
The method for producing core-shell type silica nanoparticles of the present invention comprises a copolymer (A) having an aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group and a hydrophobic organic segment (a2). A step of precipitating silica (B) in the presence of an aggregate formed in an aqueous medium. Furthermore, after having formed the silica by the said process, when it has the process of performing the sol-gel reaction of organosilane, polysilsesquioxane can also be introduce | transduced.

  In the production method of the present invention, first, a copolymer (A) having an aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group and a hydrophobic organic segment (a2) is treated with an aqueous medium. Dissolve in. Thereby, the aggregate | assembly which has a core-shell structure can be formed by self-organization. The core of the aggregate is mainly composed of the hydrophobic organic segment (a2), the shell layer is composed mainly of the aliphatic polyamine chain (a1), and the hydrophobic organic segment (a2) Hydrophobic interactions are thought to form stable aggregates in the medium.

  The aqueous medium for forming the aggregate is not particularly limited as long as it contains water and can form a stable aggregate, and examples thereof include water and a mixed solution of water and a water-soluble solvent. When using a mixed solution, the amount of water in the mixed solution may be such that the volume ratio of water / water-soluble solvent is in the range of 0.5 / 9.5 to 3/7, and 0.1 / 9.9. A range of ˜5 / 5 is more preferable. From the viewpoint of productivity, environment and cost, a mixed solution of water and alcohol may be used, but it is preferable to use only water.

  The concentration of the copolymer (A) in the aqueous medium may basically be within a range where the coalescence of the aggregates does not occur, but usually the concentration range is 0.05 to 15% by mass, A preferred concentration range is 0.1 to 10% by mass, and a most preferred concentration range is 0.2 to 5% by mass.

  Formation of the aggregate by self-assembly of the copolymer (A) in the aqueous medium in the present invention is simple in terms of process, but using an organic compound having two or more functional groups, It is possible to crosslink the polyamine chain (a1) of the shell layer, and it is also possible to obtain an aggregate-like one. For example, an aldehyde compound having two or more functional groups, an epoxy compound, an unsaturated double bond-containing compound, a carboxyl group-containing compound, or the like may be used.

  The method for producing core-shell type silica nanoparticles of the present invention comprises a step of forming a silica, ie, a step of performing a sol-gel reaction of a silica source using the association in the presence of water as a template in the presence of water, following the association formation step. Furthermore, polysilsesquioxane can also be contained in the core-shell type silica nanoparticles by further performing a sol-gel reaction using organosilane after silica deposition.

  As a method for performing the sol-gel reaction, core-shell type silica nanoparticles can be easily obtained by mixing an aggregate solution and a silica source. Examples of the silica source include water glass, tetraalkoxysilanes, tetraalkoxysilane oligomers, and the like.

  Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and tetra-t-butoxysilane.

  Furthermore, tetramethoxysilane tetramer, tetramethoxysilane heptamer, tetraethoxysilane pentamer, tetraethoxysilane decamer and the like can be mentioned.

  The sol-gel reaction that gives the core-shell type silica nanoparticles does not occur in the continuous phase of the solvent but proceeds selectively only in the aggregate domain. Accordingly, the reaction conditions are arbitrary as long as the aggregate is not disassembled.

  In the sol-gel reaction, the amount of silica source relative to the amount of aggregate is not particularly limited. Depending on the composition of the target core-shell type silica nanoparticles, the ratio of the aggregate to the silica source can be appropriately set. In addition, when the structure of polysilsesquioxane is introduced into the core-shell type silica nanoparticles using organosilane after silica deposition, the amount of organosilane is 50% by mass with respect to the amount of silica source. Or less, more preferably 30% by mass or less.

  Examples of the organic silane that can be used when polysilsesquioxane is introduced into the nanoparticles include alkyltrialkoxysilanes, dialkylalkoxysilanes, and trialkylalkoxysilanes.

  Examples of alkyltrialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, and iso-propyltrimethoxysilane. , Iso-propyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycitoxypropyltrimethoxysilane, 3-glycitoxypropyltriethoxy Silane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltomethoxysilane, 3-mercaptotriethoxysilane, 3,3,3- Rifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, p- Examples include chloromethylphenyltrimethoxysilane and p-chloromethylphenyltriethoxysilane.

  Examples of dialkylalkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, and diethyldiethoxysilane.

  Examples of trialkylalkoxysilanes include trimethylmethoxysilane and trimethylethoxysilane.

  The temperature of the sol-gel reaction is not particularly limited, and is preferably in the range of 0 to 90 ° C, and more preferably in the range of 10 to 40 ° C. In order to efficiently produce core-shell type silica nanoparticles, it is more preferable to set the reaction temperature in the range of 15 to 30 ° C.

  The sol-gel reaction time varies from 1 minute to several weeks and can be arbitrarily selected. In the case of methoxysilanes having high reaction activity of water glass or alkoxysilane, the reaction time may be from 1 minute to 24 hours, and the reaction efficiency is improved. Therefore, it is more preferable to set the reaction time to 30 minutes to 5 hours. In the case of ethoxysilanes and butoxysilanes having low reaction activity, the sol-gel reaction time is preferably 5 hours or more, and the time is preferably about one week. The time for the sol-gel reaction with organosilane is preferably in the range of 3 hours to 1 week depending on the temperature of the reaction.

  According to the production method of the present invention, core-shell type silica nanoparticles having a uniform particle size that do not aggregate with each other can be obtained. The particle size distribution of the obtained core-shell type silica nanoparticles varies depending on the production conditions and the target particle size, but is ± 15% or less with respect to the target particle size (average particle size). Can be produced within a range of ± 10% or less.

  As described above, unlike the conventional core-shell type silica nanoparticles, the core-shell type silica nanoparticles production method of the present invention differs from the conventional core-shell type silica nanoparticles in that the shell layer silica matrix is highly reactive with primary amino groups and / or two. An aliphatic polyamine chain (a1) having a secondary amino group is introduced, and the particle diameter is in the range of 5 to 100 nm, particularly 5 to 30 nm, and core-shell type silica nanoparticles excellent in monodispersity can be produced. Since the obtained core-shell type silica nanoparticles can be modified with polysilsesquioxane, application as a resin filler or abrasive filler can also be expected.

  In addition, the core-shell type silica nanoparticles of the present invention have a highly reactive primary amino group and / or aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group present in a composite form in the silica matrix of the shell layer. Thus, various substances can be immobilized and concentrated, and the hydrophobic organic segment (a2) present in the core layer can be functionalized. As described above, the core-shell type silica nanoparticles of the present invention are capable of selectively immobilizing and concentrating metals and biomaterials in nano-sized spheres, and functional molecules can be modified inside the particles. It is a useful material in various fields such as biotechnology field and environment-friendly product field.

  The production method of the core-shell type silica nanoparticles of the present invention is extremely easy as compared with the production methods such as the known Stover method that is widely used, and the core-shell type silica nanoparticles that cannot be produced by the Stover method can be produced. The application has great expectations regardless of the type of business or domain. In addition to the general application area of silica materials, it is also a useful material in areas where polyamines are applied.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples. Unless otherwise specified, “%” represents “mass%”.

[Evaluation of chemical bond between copolymer and silica by NMR measurement]
¹ H-NMR measurement (manufactured by JEOL Ltd., AL300, 300 Hz) was performed on the synthesized copolymer (A) to identify the chemical structure. In addition, solid ²⁹ Si CP / MAS-NMR (manufactured by JEOL Ltd., JNM-ECA600, 600 Hz) is performed using the core-shell type silica nanoparticle powder, and the condensation degree (Q4, Q3, Q2) of silica is evaluated. did.

[Observation with transmission electron microscope]
The synthesized dispersion of silica nanoparticles was diluted with ethanol, placed on a carbon-deposited copper grid, and the sample was observed with JEM-2200FS manufactured by JEOL Ltd.

[Evaluation of particle size and core-shell structure by small-angle X-ray scattering]
The silica nanoparticle powder was measured by small angle scattering (manufactured by Rigaku, TTRII), and the particle size was estimated by NANO-Solver analysis of the scattering curve.

[Evaluation of composition by TGA measurement]
The silica nanoparticle powder was subjected to TGA measurement (TG / DTA6300, manufactured by SII Nanotechnology Co., Ltd.), and the particle composition was estimated by mass reduction in the range of 150 to 800 ° C.

Synthesis Example 1 <Synthesis of Copolymer (A-1)>
1.5 g of branched polyethyleneimine (SP003, Nippon Shokubai Co., Ltd., average molecular weight 300) and 0.5 g of glycidyl hexadecyl ether (Aldrich reagent, hereinafter referred to as EP-C ₁₆ ) were dissolved in 40 mL of ethanol. The reaction was carried out at 75 ° C. for 24 hours. Ethanol was removed, and a copolymer (hereinafter referred to as A-1) was obtained through vacuum drying at 60 ° C. ^{By 1} H-NMR measurement, a signal derived from a proton adjacent to ether oxygen (3.0 to 4.0 ppm) was broad, and thus the formation of the copolymer (A-1) was confirmed.

A copolymer (hereinafter, A-2 to A-13) was synthesized using the method shown above. Table 1 shows the mass ratio of the raw materials used. SP003, SP006, SP012, SP018, SP200 and P1000 are branched polyethyleneimines (manufactured by Nippon Shokubai Co., Ltd.), and the average molecular weights are 300, 600, 1200, 1800, 10,000 and 70,000, respectively. The average molecular weight of polyallylamine (PAA) is 15,000 (manufactured by Nittobo). 2-Ethylhexyl glycidyl ether is a reagent (hereinafter referred to as EP-C ₈ ) manufactured by Tokyo Chemical Industry Reagents.

Example 1 <Synthesis of core-shell type silica nanoparticles>
An aggregate was obtained by stirring a mixed solution of 0.05 g of copolymer (A-8) and 5 mL of water at 80 ° C. for 24 hours. To the dispersion solution of this aggregate, 0.50 mL of MS51 (methoxysilane tetramer) was added as a silica source. The obtained dispersion solution was stirred at room temperature for 4 hours, then washed with ethanol and dried to obtain a powder. As a result of estimation from TGA measurement data, the organic component content in the powder was 17.3%. It was confirmed by TEM observation that the obtained powder had a core-shell structure (FIG. 1). The core with a center of 3.5 nm is considered to be a hydrophobic organic segment having a relatively low electron density, and appears bright. On the other hand, the 4 nm shell layer is considered to be a complex of an aliphatic polyamine having high electron density and silica, and looks dark. Moreover, the shape of the obtained powder was a sphere excellent in monodispersibility, and the particle size was ˜11 nm.

  The powder obtained in Example 1 was evaluated by X-ray small angle scattering measurement. As calculated from the scattering of the sample, the particle size, core size and shell thickness were 11.9 nm, 3.1 nm and 4.3 nm, respectively. This almost coincides with the result of TEM observation.

^Further, by using the 29 Si CP / MAS-NMR, it was evaluated chemical bonding of the silica in the powder. As a result, the integrated areas of Q4, Q3 and Q2 of the silica network were 45.5%, 51.9% and 2.6%, respectively. The overwhelming presence of Q4 and Q3 suggests that the polyamine which is the shell of the aggregate of the copolymer (C) functions as a catalyst / scaffold for the sol-gel reaction. From the above, it was confirmed that the powder obtained in Example 1 was the core-shell type silica nanoparticles of the present invention.

Example 2-16
Core-shell type silica nanoparticles were synthesized using the method for producing aggregates and the sol-gel reaction conditions of silica source shown in Example 1. The results are shown in Table 2. The sol-gel reaction was performed at room temperature for 4 hours. The average size and shape confirmation are the results of TEM observation. TEM photographs of the core-shell type silica nanoparticles of Example 5, Example 8, Example 11 and Example 12 are shown in FIGS. 2, 3, 4 and 5, respectively.

Comparative Example 1
Using branched polyethyleneimine (SP200, manufactured by Nippon Shokubai Co., Ltd., average molecular weight 10,000), aggregate formation and silica precipitation were performed in the same manner as in Example 1. As a result, the entire solution was gelled. Since the hydrophobic segment is not bonded to the branched polyethyleneimine, it is impossible to form an aggregate as a template in the sol-gel reaction of silica source, and it is impossible to form core-shell type silica nanoparticles.

Comparative Example 2
According to the method shown in JP 2010-118168 A (Synthesis Example 1), hydrophilic polyethylene glycol (average molecular weight 5,000) was bonded to branched polyethyleneimine (average molecular weight 10,000) (ethyleneimine unit) The molar ratio of ethylene glycol units is 1: 3). Using the obtained copolymer, aggregate formation and silica precipitation were carried out in the same manner as in Example 1. As a result, the entire solution was gelled. Since polyethylene glycol is hydrophilic, a core-shell aggregate having a hydrophobic core cannot be formed by hydrophobic interaction in water. Turn into.

Example 17 <Synthesis of core-shell type silica nanoparticles under neutral conditions>
An aggregate was obtained by stirring a mixed solution of 0.05 g of the copolymer (A-1) and 5 mL of water at 80 ° C. for 24 hours. The pH of the dispersion solution of the copolymer (A-1) aggregate was adjusted to around 7.0 using an aqueous solution of hydrochloric acid. 0.50 mL of MS51 was added as a silica source to the aggregate dispersion thus obtained. After the mixed solution was stirred at room temperature for 4 hours, a nanoparticle sol solution was obtained. The sol solution is transparent and has high sol stability at room temperature. The sol solution was diluted with ethanol to prepare a sample for TEM measurement. By TEM observation, formation of core-shell type silica nanoparticles excellent in dispersibility could be confirmed (FIG. 6). The particle diameter, core size and shell layer thickness of the particles were 10 nm, 3 nm and 4 nm, respectively.

Example 18 <Synthesis of polysilsesquioxane modified core-shell type silica nanoparticles>
After silica precipitation in Example 1, 0.1 mL of trimethylmethoxysilane was added to the dispersion. The resulting solution was stirred at room temperature for 24 hours, washed with ethanol and dried to obtain polysilsesquioxane-modified core-shell type silica nanoparticles. By TEM observation, formation of spherical core-shell type silica nanoparticles having a particle size of 13 nm and excellent monodispersibility was confirmed.

Claims (8)

The hydrophobic organic segment (a2) portion of the copolymer (A) having an aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group and a hydrophobic organic segment (a2) as a main component A core layer to
A shell layer composed of a composite composed mainly of the aliphatic polyamine chain (a1) and silica (B);
A core-shell type silica nanoparticle characterized by comprising: The core-shell type silica nanoparticles according to claim 1, further comprising polysilsesquioxane (C) in the shell layer. The core-shell type silica nanoparticles according to claim 1 or 2, wherein the shell layer is formed by complexing the aliphatic polyamine chain (a1) with a silica (B) matrix. The core-shell type silica nanoparticles according to any one of claims 1 to 3, wherein the aliphatic polyamine chain (a1) is a branched polyethyleneimine chain or a polyallylamine chain. The hydrophobic organic segment (a2) is at least one hydrophobic organic segment selected from the group consisting of polystyrene, polyacrylate, polyurethane having a polymerization degree of 5 or more, and a compound having an alkylene chain having 5 or more carbon atoms. The core-shell type silica nanoparticles according to any one of claims 1 to 4. The core-shell type silica nanoparticles according to any one of claims 1 to 5, which have an average particle diameter of 5 to 30 nm and are monodisperse. A copolymer (A) having an aliphatic polyamine chain (a1) having a primary amino group and / or a secondary amino group and a hydrophobic organic segment (a2) is mixed with an aqueous medium, and the hydrophobic organic segment (a2) Characterized in that it comprises a step of forming an aggregate comprising a core layer composed mainly of an aliphatic polyamine chain (a1) and a shell layer composed mainly of an aliphatic polyamine chain (a1), and performing a sol-gel reaction of silica source using the aggregate as a template. A method for producing core-shell type silica nanoparticles. Furthermore, the manufacturing method of the core-shell type silica nanoparticle of Claim 7 which has the process of performing the sol-gel reaction of organosilane.